Alright tomorrow I’ll pull everything out so I can test the cells. Anything I should know so I dont break it? How do I remove it with the glue on the bottom and fo I just unplug the cables from the bms, can I break the bms if I unplug the wrong cables in order? (Onewheels are like that)
Use the paint scraper and mallet to hit the glue on the edge of the cell holders on the bottom just to free it up a bit. If a temp sensor pulls out it doesnt matter.
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Battery is out and tomorrow I’ll reattach the nickel sheet. I am going to solder it since I dont have a spot welder, is that ok? How do I I go about testing each group, I just dont wanna screw something up that is avoidable.
Turn cells on side and use a multimeter to measure each set of cells…
I have a pack where I solder a full row as the entire row was dead. You need to be careful not to overheat the cells and use some flux so the solde binds easily to the nickel and cell.
So the plot thickens…
I have 2 bad BMS that even if placed in a good battery won’t come to life. They report e029 when plugged into the charger. On closer inspection I found that each row of cells has a self healing fuse, they were all intact and happy…
However there are 2 permanent fuses (F1 and f2) which are blue… On both bad BMS f2 seems to be blown.
I haven’t tested a BMS that can communicate and turn on that goes to red led’s yet, and I also have tested a fully working BMS/battery yet. But still some interesting info…
I have a new battery showing red lights. Curious if you’ll be able to revive the BMS/fuse on them and get the batteries back to work.
No luck soldering. Solder just wouldn’t stick to the cells. Going to buy a spot welder
Did you use flux? Without flux it won’t stick.
I put flux down. The solder would hit the flux and sizzle the flux turned brown then I’d let go and the metal would try and go back to its original bent shape and rip the solder off. I dont have the optimal solder set up and spot welding looks like effortless magic and if I am going to open a few more batteries I might as well get one. Do you by chance know the thickness of the nickel. It looks very thick which would require a bigger welder.
The solder just wanted to stick to the iron so I couldnt pull it off and let it sit on the cell since it would follow the iron then it would just be a ball around the nickel tab but floating above the cell
Btw did some testing while I wait to get a spot welder.
The big terminals give 5.4v and the top group does 2.17v
I wasn’t able to test every single one but the rest were about 0.15v
Can anything even be done? And how can I charge them since like I dont have one of those dc supplies
Here’s a very good article on Li-ion batteries and in a round about way explains why a good BMS will shut down the battery permanently if some cells have gone too low:
Get (a second hand) one or find somebody who has one…
At these voltages the battery shouldn’t be charged, it should be scrapped since any cell gone that low will have irreparable damages. A super slow charge might revive some kind of capacity but this creates risks for fires later on so it’s best to avoid this.
so it’s good or no? i do now that 0v often means it’s been cutoff which is a good thing but the fact it’s 0.1v
i was just gonna charge up one single cell and see if it seems to show life and if not scrap the cells
If a row of cells is under 1.5V for more than a week they are no good. In that case you will need to remove the cells and replace.
dang well this battery is over a year old and remember it was never even used.
in that case i could open my unplugged battery (which has since stopped blinking)
so it might have the same problem. if i could just harvest the bms or maybe salvage some cells from it and merge the batteries?
if that is a loss then i have the other red battery which im not convinced was unplugged but since it happened 2 weeks ago it still has charge however was all the way dead when last used so it wont have much charge left. if it’s not the fuse then ill swap the bms with the never used battery and hopefully can revive at least one
Ok so while the output of the battery currently cut open is 5.4v I tested my other “dead” battery which was unplugged while still on and it reads 0.4v I then tested my other red battery which unconfirmed or not if it was unplugged which red which outputs 3.5v.
THEN I tested two fully working batteries that flash green and everything which output 0
So a working battery isnt supposed to read anything is it? What could be causing the current to be readable on the broken ones? Is it simply the thing you can hear click inside the battery on power on and off that just needs to be flipped?
Where are you measuring these voltages?
From the main massive terminals near the bms and the metal sheets over the groups. Perhaps that’s not correct?
For the other batteries I was testing them in the main plug from the outside
- Outside plug should sit at 0V as the relay should be cutting off voltage. If it’s not, it would be interesting to know if that was the start of the issue. It may be that unplugging under power (board or charger) breaks the relay.
- Main terminals should read full battery voltage
- To read each metal sheet you need to entirely remove the battery. Or if your probe is small enough, you can get it down the side of the battery and onto the balance solder joint of each row of cells.